Deposition of thin films on a substrate surface is an important process in a variety of industries including semiconductor processing, diffusion barrier coatings and dielectrics for magnetic read/write heads. In the semiconductor industry, in particular, miniaturization requires high level control of thin film deposition to produce conformal coatings on high aspect structures.
As well known in the art, a silicon oxide film has been mainly used as a material of a gate insulating film in MOSFETs, and a polysilicon film has been used as a material of the gate. However, as the integration level of the semiconductor devices becomes higher, it is required that the line width of the gate and the thickness of the gate insulating film be reduced. In the case where a silicon oxide film is used as the material of the gate insulating film, if the thickness of the gate insulating film is too thin, the insulating characteristic is not stable since the leakage current due to a direct tunneling through the gate insulating film becomes greater. Recently there has been an effort to use a high dielectric constant material, having a relatively higher dielectric constant than a silicon oxide film, as the material of the gate insulating film. Also, in order to minimize the polysilicon gate depletion effect, there has been an effort to use a metal gate instead of the polysilicon gate.
As such, there is a need for improved methods of depositing suitable N-metals for such applications. Chemical and physical vapor depositions have been methods well-known to deposit such films. Another method for deposition of thin films is atomic layer deposition (ALD). Most ALD processes are based on binary reaction sequences, where each of the two surface reactions occurs sequentially. Because the surface reactions are sequential, the two gas phase reactants are not in contact, and possible gas phase reactions that may form and deposit particles are limited. While ALD tends to result in more conformal films than traditional chemical vapor deposition (CVD), prior art processes for ALD have been most effective for deposition of metal oxide and metal nitride films.
Tantalum, TaxCy and TaxAlyCz films show much potential as n-metals. Thus, there is a need for a method that can deliver Ta precursors to deposition reactors and enable the deposition of specific desirable film compositions comprising Ta.